Sandblast gun



Aug. 8, 1950 S. MOREL SAND-BLAST GUN Filed Dec. 17, 194e S. NN j, a,

N Re Patented Aug. 8, 1,5950

`sillvnmis'r GUN Stanislas Morel, Paris,` France In France December 29, 1945 Applicationnecember 17, 1946, serial No. 7176.811

In small sand-blasting operations, both in the open air and in a booth or under a tarpaulin, use is often made of sand-blasting"by suction owing toits simplicity. l

It is known that sand-blasting by suction is effected by means of compressed air with a gun which is constructedon the principle of the blast pump. The compressed air is supplied to a tube called injector, the jet of air passes through the body of the gun and issues through a tube called nozzle, causing a rarefaction of the air in the said body of the gun. f Owing to the vacuum thus created, va stream of atmospheric air is produced in another tube connected to a source of abrasive and conveys the abrasive into said body where it is projected by the compressed air through the nozzle against the surface to be treated.

In the known sand-blast guns, the injector has to be very remote from the nozzle'in order not to be worn away 'by the abrasive which issues into the body of the gun almost at'right angles to the axis of said injector.

The great distance which` it is necessary to leave as a. safety measure between the injector and the nozzle, makes it lnecessary to give to said nozzle a passage cross-section yequal to at least four times that of the injector in order to enable the jet of compressed air, in spite'of its divergence as it issues from the injector, to penetrate into the nozzle without creating eddies in the body of the gun, otherwise there would be no vacuum.

This great difference. of cross-section between the injector and the nozzle causes a considerable loss of pressure and does not' permit of a vacuum of more than about eighteen centimetres of mercury to be obtained; consequently the suction of atmospheric air, the force of which is propor- P tional to the vacuum, is very small; this air therefore only conveys a small quantity of abrasive, the speed of which .is moreover braked by the sudden change of direction which it has to effect'in the body of the gun before penetrating -i l into the nozzle.

For these various reasons, blast guns are of low efficiency.

The present invention has for the --known sandits object to provide an improved sand-bla'st-gun of vhigh efliciency, which is very practical to use, and, with this object in view, the gun according to the inventionA comprises a compressed air injector tube which terminates just short of the Vconverging coneof the neck ,for the. discharge nozzle forthe Il mixture of compressed air and abrasive, thereby 4 claims. (rc1. 51-11) .element 1 forming the injector.

enabling said nozzle to be given a cross-sectional area which is hardly equal to three times that of the injector. Consequently the loss of pressure y in the nozzle is not great and the efficiency is considerably increased, a fortiori since, owing to the fact that the injector tube terminates near the mouth of the discharge nozzle neck, the vacuum created is of the order of forty cm. of mercury. Due to thishigh vacuum there is a very powerful stream of atmospheric air which is `capable of sucking up a very large quantity of abrasive, even more than is required.

According to another feature, the body of the gun is very short and of frusto-conical shape in order to lighten it, to reduce the length of the injector tube so as to decrease the loss of pressure, and facilitate the flow of the abrasive to the discharge nozzle. y

Further features of the invention will be apparent from the following description, with ref erence to the accompanying drawing, which is given solely by way of example, and in which: Fig. 1 is an elevational view, with parts in section, of a sand-blast gun according to the invenion;

Fig. 2 is a partly sectional plan view thereof;

Fig. 3 is a longitudinal section of a variant of the abrasive sucking device or abrasive pickup, fitted at the bottom of an abrasive container;

Fig. 4 is a view of the rear face of a modification of the head of the gun.

According to `the embodiment illustrated in Figs. land 2, the gun comprises a frusto-conical metal injector body 1, the axis of which is at XX and which is lclosed at the rear by a head 2 -ilxed by screwing or otherwise.

At the front of the body l are fixed, for ex`' ample by means of a nut 3, a nozzle neck 4 provided with a passage 5 flaring inwardly on its outlet end toward the body l and a tubular nozzle 6 of larger internal diameter d1 than the 'diameter d2 ofthe neck 4 on the'outlet side.

The neck 4 and the nozzle 6 are made of any very hard metal or alloy, in particular of tungsten carbide, boron, etc. orare internally lined with a liner of one of these substances or of like substances. y

In the body l and carried by the head 2 along the longitudinal axis XY is arranged a tubular This injector tube is fixed at the centre of the head in order to facilitate the centring thereof, which must be very accurate. Its front end lilterminates very near the entrance to the neck l4, for examples.

few millimetres from its inlet. The internal cross-section of the injector tube is of the order of one third to one half of the cross-sectional area of the nozzle. For a normal nozzle of diameter 61:10 mm., the diameter d3 of the injector tube is preferably between 6 and 7 mm. The rear end of the injector tube is attached by forcing, screwing or otherwise fixing the same, in an axial passage 9 of the head 2. Said passage 9 opens into a radially'extending chamber lil.- chamber ID is screwed, Welded or otherwise fixed in a fluid-tight manner, a rigid tube which is preferably perpendicular to the axis XX. Said" tube opens into the body I2 of a plug-cock; The plug I3 of said cock is provided with a longitudinal chamber |4 which. can be placed in communication with the tube I'I-rthrougl'i, aY hole l5:

In order to enable it to be rotated, the plug i3.

which emerges from the body l2 carries an 0p-s erating member, for example a wheel |51. wheel comprises for example a disc of rubber or likeA` material clamped' between two washersvi Fl-llbya'f nut`v |912 ItE shouldbe noted'that the washerl |6`4 could bein'adel-of metal and; in'that case; preferably serrated orf knurled at'l its periph# ery;l The rotation-ci"l the plug-visl-limited for examplebyaprojection 2l)T carried-bythe body |21 and'housedinacircumferential slot 27| of limited lngthcprovi'dedf in the plug |32 in suchaafmanner that by rotating said plug-, iti-is possible at will tov movetheholei into-register withthe tube |`i or to shut* 01T the communication between said 'tube and the duct i4 ofthefplug* |3-l Said duct |'4L is' permanently in communicathrough' a preferablyfflexible orv pliable tube 22.; with" asource not shownfof compressed air or other compressed gaseous-uid.

The head Zisprovided; on each side of the hole 9 and extending right throughv it parallelv tothe axis XX; with two holes 23 in which are fixed on the* outer rear4 face'Y of' the head' two tubes.

Each of. saidltubesvv 2'4ha's one or more holes proyidedtherein which,Y atA will; can either be made to open into the atmosphere" or, on the contrary, beclosed by means of .a sleeve Ziadapt' ed' tovslide. or rotate.. on said tube;

Atitsrear. end, .each tube' 2'4is' connected by a preferably flexible or. pliable'pipelz'l made of rubber or other material, to a metal tube 28* which abutsagainstatubular extension 29. The abut'- ting ends of the tubes 28`and 213are'screw threaded and. are connected together by the tapped end oi asleeve 3'6. Said sleeve 3@ is provided withta number ofi air inlet holes 3l; In. said sleeverisfscrewed at.32',V concentricall'y'. tothe tube 29, another tube 33, the internaldiameter of whichris lar-gerthan the external diameterjoff the tube 29;;soas to/provideibet'ween these two tubes anannulan space 34. Thisannul'ar space 34 can i. communicate withA the atmosphere` .through the holes: 35|; of the-sleeve 3.0. by meansy of` holes 35 whiclr are; provided in the tube-33 and with which; by..r adjusting: thesleeveY 30, the holes-l 3| In saidL said' can! bef brought' more: or: less intoregister, the

atliu'st'm'entv whichfhasbeen madeibeing,v retained bye means ofianut 3B screwed onithe tube' 33. At the rear end, the space 34 is normally. operrl Tlietube 33'?v terminates;` at the rear: int ahumb'erof' divergent tong-ues 3l". Furthermoregitiis kept centered on theitub'e 29y by screws 38T bearingagainst'said tube'.

Irr Fig. 1f, the flexible tube 22 hasbeen. shown lient back` against the tubes 21%; itrcan be xed .f 4 thereto by means of a collar 39 or any other appropriate means.

The apparatus operates as follows:

The rear end of the tubes 29 and 33 dips into a heap of abrasive 40 which may be open the atmosphere. Owing to the divergent parts 31 there is no danger of the rear end of the space 34 between the tubes 29 and 33 being obstructed, for example by theI ground 4| or a wall such as 42.

The is heldiin onehandlbythe rigid tube the tubes 21 and 22"resting-on the' forearm. As soon as the cock |3 is opened, the operation of said cock being very easily effected since it is onlynecessary to rub the wheel I6 against any surface, for example against the part to be sandblastedV orV against the palm of the other hand (similarlyifor, closing the cock), the compressed air. issuesv from the injector tube l and flows into the nozzle 5. A vacuum is immediately created in the bodyfl and consequently a stream of atmospheric air flows through the tubes 24, penetrates through. the holesfl: and-35 flows into-the annular spacev 34. in the-direction ofi the` arrows fi,- then into. the'heap` of abrasive'r40and returns through the inside of the tube 29;: this"air;therefore-carries abrasivefrwith it. The'mixture of; air and abrasiveA flows atY a: certain. speedthrough the pipes 24intofthe body of'thefgun; parallel to and round the injector tubev 1'- and; withoutbeing subjected toA any brakingand still bythe action` of. the: stream of7^ atmospheric air" sucked in,l ows throughL the; neck; 4f towardsl thef noz-` zlerG. lItpenetrates intoisaidnozzle and mixes withv theA compressed .airfwhich issi'ssuingfrom: the injector;- tube` 'I` and; which carries. it along with it, enormously izrcreasingf` its speed; s and' proj eetsit againsta the; surface;-torbeftreated..

For; certainz work,y atlargev quantityy ofcompressed air and a small quantity of abrasiveA are required; forfothen'workit is'l theL opposite and sometimes afsmallfquantityfof each is necessary. Inf all cases; itz isf only necessary to adjust the supply oflcompressedairby means of'thecock |33 and the supply of abrasivezbyf adjustingthei air l sucked. in; by means of the sleeves; 26 which enableftheholestc be closedmore or less and consequently? theL suction. inthetubes 2liK to'. be brakedl more@ or "lessp Without thestream of: atmospheric air or if its volume" is insucienty. the@ abrasive pick-ups and the pipes 24` would'. becomey clogged With abrasivefandthe:gunr would only discharge compressed-air; On the other hand, if; the stream of atmospheric air sucked in and of abrasive are not correctly' dosed; .the-discharge; of abrasive is not regular..v Acorrectoperation of: each abrasive pick-up is ensuredbyuthe: sleeve 3e which serves tof open on' closetheifholesf 31|: more or less: ac:- cording; to-thefglneness. andi the density of the abrasive usedlA In.. certain cases;` the parttreatedrhas` toi` have the: dust removed and-.for'thisrpurpose itis; only necessary for'th'ezholes 25 to be completely uncovered; Iso; thaty noiabrasivefis sucked up and the nozzle of: the.: gun operates as a,` clusty removing blower,

As alreadystat'edthe: cockV |3 can kbe actuated quickly by rubbing'thawlieelf |62 in. the; required direction against the 4workzta'ble; y againstvthe; part to' be Y treated orf againstv the hand Vwhichf is free'. Gwingto: the speedaofi` the'.operation,l this method of'v proceed-ing prevents wasting an appreciable quantity of; compressed:` air` and: abrasive;n it also saves. time:

Sinceithezcompressed airpipe andtheti abrasive pipes are preferably fastened together, as shown, over a certain length from the gun, this is very convenient for the user. The two movable abrasive pick-ups may also be fastened together in order to facilitate the manipulation thereof.

Fig. 3 shows a modification of an abrasive pickup intended to be fixed `to the base of a hopper 43. In this case, the tube 33 is screw-threaded at its rear end at 45 and screwed in a tapped connection 46 provided for this purpose on the hopper 43.

Finally, Fig. 4 shows a rear View of a modification of the head 2, in which an opening 41 is provided which opens into the atmosphere and can be partly or completely opened or closed at will by means of a shutter 48 which is adapted to swing about a pivot 49 (or to slide). This device can replace the holes 25 of the tubes 24 and the sleeves 26.

Naturally, the invention is in no way limited to the embodiments illustrated and described which have only been chosen by way of example.

In the example of Figs. l, 2 and 4, two abrasive supplies have been provided, but of course, the device could be provided with a single supply or more than two.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A suction operated sandblast gun comprising a hollow injector body having an outlet orifice, said injector body tapering toward said oriiice a discharge nozzle neck in said orifice along the longitudinal axis thereof and having its internal wall flaring outwardly in the direction of said body, an injector tube supported by said body and extending along the horizontal axis thereof for substantially its whole length, but terminating just short of said neck, means for supplying fluid under pressure to said injector tube, and means operated by the suction effect of said injector tube for supplying abrasive to said body, in a direction substantially parallel with the axis of the injector tube, said means comprising at least an abrasive supply conduit -extending into said body, said conduit having at least one opening in the wall thereof leading to the atmosphere, and a sleeve movable on said conduit for controlling the effective area of said opening during the operation of said gun.

2. A suction operated sand-blast gun as claimed in claim 1, wherein said injector body is formed with at least one opening leading to the atmosphere and further comprising a movable shutter for controlling the eilective area of said opening.

3. A portable, suction operated sandblast gun comprising an injector body having an outlet orice, the internal wall of the body tapering toward said orifice, a discharge nozzle neck fitted in said orifice along the longitudinal axis thereof, the wall of the discharge passage of said neck flaring outwardly towards the wall of the injector body and substantially merging with said wall 'til of the injector body; an injector tube extending forwardly from the rear wall of said injector body substantially `along the horizontal axis thereof for substantially the Whole length of said body, but terminating short of the inlet end of said discharge nozzle neck, the cross sectional area of said nozzle neck being at least equal to three times the cross sectional area of said injector tube, means for supplying compressed air to said injector tube and means including a conduit for delivering abrasive to said body under the suction effect of said injector tube in a direction substantially parallel to said injector tube, said conduit being laterally offset from said injector tube, said means for supplying compressed air including an air ycontrol cock radially spaced from the injector body, and a nipple connected to said body, said nipple extending from said body at substantially right angles to the longitudinal axis of said body and connecting said body and cock, said nipple forming a hand hold for manipulating said gun.

4. A suction operated sandblast gun comprising an injector body having an outlet oriiice, the internal wall of the body tapering toward said orifice, said orifice being internally counterbored to provide a shoulder, a discharge nozzle neck tted in said counterboreand seated against said shoulder, the wall of the discharge passage of said neck flaring outwardly towards the wall of the injector body and substantially merging with said wall, a supplementary nozzle seated against said discharge nozzle and having an internal diameter greater than that of the discharge'nozzle and means for supporting said supplemental nozzle on the injector body; an injector tube extending forwardly from the rear wall of said injector body substantially along the horizontal axis thereof for substantially the whole length of said body, but terminating short of the inlet end of said discharge nozzle neck, the cross sectional area of said nozzle being at least equal to three times the cross sectional area of said injector tube, means for supplying compressed air to said injector tube and means including a conduit for delivering abrasive to said body under the suction effect of said injector tube in a direction substantially parallel to said injector tube, said conduit being laterally offset from said injector tube.

STANISLAS MOREL.

REFERENCES CITED The following references are of record in the file of this :patent:

UNITED STATES PATENTS Number Name Date 839,483 Kelly Dec. 25, 1906 844,046 Radell Feb. 12, 1907 999,485 Carolin Aug. l, 1911 1,605,617 Ruemelin p Nov. 2, 1926 2,133,149 Poncelet Oct. 11, 1938 2,369,576 Keefer Feb. 13, 1945 

